1. Field of the Invention
This invention relates to an ophthalmic photographing apparatus, and more particularly to the focus detection of a retinal camera.
2. Related Background Art
Generally in an apparatus for observing or measuring an eye, it is very difficult to focus the apparatus on the fundus oculi, due to the deficiency of the quantity of light and the badness of contrast attributable to the low reflectance of the fundus oculi. Particularly, when observing the image of the fundus oculi by the use of fluorescence or infrared fluorescence, the image of the fundus oculi being observed lacks a feeling of color (the image becomes black and white when the observation system is a TV monitor) and therefore it is difficult for contrast to be given to the image and it is more difficult to focus the apparatus (a photographing optical system and an observation optical system) on the fundus oculi.
As described above, in an ophthalmic photographing apparatus such as a conventional retinal camera, there has been the inconvenience that it is difficult to focus the apparatus on the fundus oculi.